1. Technical Field
The invention relates to an apparatus for producing picture element groups in space, to designs of such an apparatus and to methods for producing picture element groups in space as realized by such apparatus.
“Picture element groups” are arrangements of picture elements which are similar in geometric appearance and which can be varied with respect to location, size and orientation. They are specified by a corresponding number of parameters and produced by adapted devices in deflection systems. The picture elements of a picture element group are made into a group pursuant to a given general instruction and simplify the scope and time involved in the formation of the overall image. This results in an image with greater informational content achieved by a relatively lower amount of technical effort.
2. Prior Art
DE 2622802 C2 discloses a 3D display for generating picture elements in a cylindrical space which as a whole produce real 3D images. The term “real” here means that the spatial laser picture, in contrast to 3D representations, floats in an apparently empty space on flat screens or in stereoscopic images. It can be viewed from all surrounding directions, like a fish in an aquarium, without the help of any optical aids. Such images are commonly referred to as “volumetric 3D displays”. The 3D image in DE 2622802 is generated by projecting a laser beam at a rotating helical surface known in practice as a “helix”. For that reason, this system is designated as a “helix-laser-3D display”.
A helix-laser-3D display in its most simple form is shown in FIG. 1. The laser 1 emits short light-induced pulses which are directed by a deflection system as image beam 2 onto the helix 6, where picture elements 10 are produced. Although the picture elements at adjacent locations x,y,z, due to the continual rotation of the helix, can only be generated a completely different points of time, they are perceived by the human eye as interconnected adjacent picture elements. The helix is made of thin, translucent material such that the image beam is scattered upwards and downwards in approximately the same possible degree of diffusion. It rotates in a transparent cylinder 7 about a rotation axis 8 at a rate of 20 revolutions per second and is invisible to the viewer. The picture elements “float” in space.
For simple demonstrations of this principle using but a few picture elements or a loop of pre-programmed spatial images one may employ an opto-mechanical deflection system. It consists of two mirrors that can be swiveled orthogonally to one another: the x-deflection mirror 3 and the y-deflection mirror 4. If necessary, a stationary tilted mirror 5 deflects the image beam onto the helix 6. The x,y,z coordinates of the desired picture element are predetermined by the computer and adjust via actuators the deflection mirrors 3 and 4 for x and y, as well as a timed pulse for the height z, which is generated at the start of a light flash of the laser 1 to correspond to the rotational angle 9 of the helix. The horizontal size of the picture element is a function of the diameter of the image beam 2 and its height is a function of the duration of the flash. Dedicated applications require a very large number of picture elements, if possible with a plurality of features. Opto-mechanical deflection systems, such as the mechanical rotational mirror described here, are inadequate for this purpose.
For military applications, the helix-laser-3D display was built by the US Navy at great technical expense and employed for different purposes (Technical Report 1793, Revision 2, October 1998, US Navy Space and Naval Warfare Systems Center, San Diego, Calif. 92152-5001). For this purpose high-performance opto-electronic deflection systems were developed. They are capable of generating 3D landscapes consisting of more than 100,000(1) minute picture elements which are refreshed more than 20 times per second, in three colors, dynamic and with variable intensity. These helix-laser-3D displays were first used for submarine navigation, later for air-traffic control and then for medical and CAD purposes as well.
For non-military applications such systems are still too costly. Even the generation of a modest number of independent and randomly variable picture elements requires a disproportionately high engineering effort for the deflection system. As already mentioned, such a system must be able to direct the image beams for every single picture element at the right time onto the desired x,y,z position and have it flashed at the correct time. Here one must always keep in mind that, due to helix rotation, each x,y,z picture element can only be generated in space at a very brief and precise moment in time. This means that the 3D image must be composed point by point in temporal succession at x,y,z positions generally located far from each other. The coordination of position and time requires a very rapid change of the image beam from every x,y,z position to every other x,y,z position located at an arbitrary distance and likewise requires a very high degree of precision in stroboscope timing and duration. The efficiency of a helix-laser 3D display is gauged by how many picture elements with which variable features (color, intensity, etc.) the deflection system is able to generate with sufficient speed and compose them into a 3D scenario. The engineering effort for deflection systems increases exponentially with the number of desired picture elements.
The 3D images are usually composed point by point from individual picture elements. Each of these is defined by its x,y,z coordinate and by additional characteristics, which must be implemented by the deflection system. This means that every single picture element demands the same degree of effort from the deflection system regardless of its importance in the overall image.
U.S. Pat. No. 5,854,613 A discloses a possibility for multiplying image beams by using translucent mirrors to distribute the beams. Here the incident light beam is divided into two emitted beams having half of the light intensity, it being possible to generate a plurality of optical beams in succession with the same drop in light intensity. Each of the resulting optical beams requires its own deflection unit. Directed toward a desired x,y,z position, each sub-beam generates a single picture element in space.